U.S. forces will 'lay siege' to the capital, then seek to break the regime, a Pentagon official says. The Iraqis shoot down two American aircraft.

WITH U.S. FORCES IN IRAQ — U.S. forces reached Saddam Hussein International Airport on the edge of Baghdad early today and positioned themselves to fight for it, commanders said.

The Americans would begin the fight "at a time of our choice," Capt. Frank Thorp told reporters at U.S. Central Command headquarters in Doha, Qatar. Correspondents traveling with forward units of the Army's 3rd Infantry Division said its troops were within six miles of the Iraqi capital.

A Pentagon official said U.S. forces would "lay siege" to Baghdad by surrounding it, taking control of its airport and seizing its bridges -- then try to break the Hussein regime without breaking the will of the majority of Baghdad residents or destroying their resources.

The advance to the Baghdad airport came after the infantry punched through one division of Hussein's Republican Guard south of Baghdad on Wednesday and Marines said they had destroyed another division to the southeast.

The Marines pushed ever closer to Baghdad from the southeast, expecting to clash with Republican Guard reinforcements moving their way. Military officials described the Iraqi units as disjointed, chaotic and lacking cohesion as a fighting force.

But the Iraqis put up some resistance. An F/A-18 Hornet jet-fighter and a UH-60 Black Hawk helicopter were shot down Wednesday, military officials said. Rescue teams searched for the jet pilot. The Pentagon said seven died on the helicopter and four were injured, but Central Command said only six people were on board, and it had no confirmation of casualties.

The U.S. advances in the 2-week-old war were significant because they brought the United States and Britain closer to the battle for Baghdad -- and the fight to oust Hussein and disarm his nation.

But the breakthroughs also meant that allied forces had penetrated the "red line" that is Baghdad's defensive perimeter, beyond which fighting is expected to be furious and U.S. commanders said Hussein might unleash chemical and biological weapons.

In Baghdad, a government official read a statement on Hussein's behalf for the second straight day Wednesday, urging the Iraqi people to rise up and defeat the allies. "They are criminals, aggressors," the statement said. Hussein did not appear.

Information Minister Mohammed Said Sahaf denounced allied reports from the battlefield as lies and insisted that Iraqi forces had pushed back "U.S. and British mercenaries" in southern Iraq.

In a broadcast from Baghdad, the pan-Arab satellite television station Al Jazeera said a U.S. missile struck a Red Crescent maternity hospital in a residential area of the capital, killing several people and wounding 25.

Central Command said it was reviewing target data for air missions at the time of the attack.

About 100 miles southeast of Baghdad, near the city of Al Kut, units of the 1st Marine Division crossed a key bridge Wednesday over the Tigris River in a thundering assault against the Baghdad Division of the Republican Guard.

By midafternoon, the Marines said they had broken the guard division as an effective fighting force and cut off its retreat.

"We're on the attack," Dowdy said. "We will continue the attack until it's over."

The Marines sidestepped Al Kut because commanders decided it was too hostile and might slow them down.

They stopped cars, trucks and buses fleeing the city and sent them back into town. They searched a busload of men but found no weapons. Instead, the Marines said, many of the passengers were carrying large amounts of money, perhaps their life savings.

On the western prong of the attack, U.S. officials said the Medina Division had been decimated and that resistance proved light and sporadic in an area that had long been considered a barrier in the campaign against the capital.

Intelligence reports said the Medina's 2nd and 14th brigades were "rendered ineffective."